8/19/2011 10:11 AM PDT

Taylor Armstrong Beaten, Camille Grammer Threatened

Taylor Armstrong secretly revealed to cast members she was beaten so badly by Russell Armstrongshe had to undergo surgery -- and when he found out she spilled the beans, he sent Camille Grammer a chilling, threatening email ... this according to multiple sources connected with the show.

We're told ... in late June, as "Real Housewives of Beverly Hills" was shooting season 2 ... Taylor was severely beaten. Sources say Russell hit her in the face so hard he cracked bones in her cheeks. Sources say there are pictures of the injuries and they are "horrific."

Taylor -- who was hospitalized as a result of the beating -- tried to keep it a secret, but she had a big problem ... she couldn't show her face for weeks, and she feared she'd be fired for appearing to be uncooperative and flaky.

We're told Taylor went home and told Russell about her conversation with the two women and the outrage they had shown when they heard what happened. Russell reacted by sending Camille a "very threatening" email. One source who read it said, "It was the rantings of a lunatic."

As for Taylor, her injuries were so bad ... shooting was delayed for several weeks.